1. Field of the Invention
The present invention relates to a subsurface formation cutter for use in connection with directional cutting into a subterranean formation.
2. Description of the Prior Art
The use of formation cutting devices is known in the prior art, and various technologies exist for recovering hydrocarbon fluids from subterranean formations. It is known to one skilled in the art that hydrocarbon fluids can be collected from a production wellbore which is positioned in a formation that contains hydrocarbon fluids. The movement of hydrocarbon fluids to the production wellbore may be driven by a multiplicity of forces, including the wellbore internal pressure, external pressurization of the formation, fluid injection drive, a combustion front (i.e., in situ combustion), and steam assisted gravity drainage (SAGD), etc.
It can be appreciated that many factors contribute to or impede the flow of hydrocarbon fluids to the production wellbore or the injection of fluid into the reservoir, such as but not limited to, the magnitude of the driving forces in the formation, the viscosity of the hydrocarbon fluids in and through the formation and the permeability of the formation especially near the wellbore. These factors contribute to the production rate of the hydrocarbon fluids and its enhanced recovery for increasing the amount of hydrocarbon fluids that can be extracted from a formation.
The volumetric sweep efficiency at any time is the fraction of the total reservoir volume contacted and removed by the driving forces during the recovery. Consideration of the mobility of the fluids is an important factor when determining the area and vertical sweep efficiency components of the volumetric sweep efficiency. The mobility of hydrocarbon fluids in a subterranean formation is the ratio of the permeability of the formation to the viscosity of the hydrocarbon fluids. Mobility is therefore a function of both the properties of the hydrocarbon fluids and the properties of the subterranean formation. As the mobility ratio varies along the wellbore, the production rate or injection rate and the sweep efficiency vary accordingly.
For a given magnitude of driving force, the flow of hydrocarbon fluids to the production wellbore may generally be expected to increase as the mobility of the hydrocarbon fluids in the formation increases, either by decreasing the viscosity of the hydrocarbon fluids or by increasing the permeability of the formation.
Known methods for decreasing the viscosity of hydrocarbon fluids in a subterranean formation include increasing the temperature of the hydrocarbon fluids in the formation and/or diluting the hydrocarbon fluids in the formation with a less viscous fluid.
SAGD process that injects steam into the formation is currently used to increase the temperature of the hydrocarbon fluids in the formation and decrease its viscosity. Additional methods of increasing the temperature of the hydrocarbon fluids are by introducing a heat source into the formation, by in-situ combustion of the formation, or the like. Diluting the hydrocarbon fluids in the formation may be achieved by injecting a diluent fluid such as a light hydrocarbon fluid or carbon dioxide into the formation. It also known to decrease the viscosity of the hydrocarbon fluids in the formation by increasing the temperature of the hydrocarbon fluids and in combination with diluting the hydrocarbon fluids.
While the above-described devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe a subsurface formation cutter that allows directional cutting into a subterranean formation where flow into the well is locally impeded or blocked by poor permeability in the reservoir or by formation damage during drilling.
Therefore, a need exists for a new and improved subsurface formation cutter that can be used for directional cutting into a subterranean formation to selectively improve the flow into the well from the reservoir, thereby, resulting in increases in production rate, well bore conformance, volumetric sweep efficiency and recovery of reservoir fluid. Technically, the cut channel effectively creates a stimulation affect on the well causing it to produce or inject more fluids either as a larger wellbore or as a wellbore with beneficial negative skin. In this regard, the present invention substantially fulfills these and other needs. The cut can be used to direct and control subsequent fracturing of the formation or as a replacement for hydraulic fracturing. In this respect, the subsurface formation cutter according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provide an apparatus primarily developed for the purpose of directional cutting into a subterranean formation.